CVE-2011-4759 in Plesk Small Business Panel
Summary
by MITRE
Parallels Plesk Small Business Panel 10.2.0 generates web pages containing external links in response to GET requests with query strings for client@1/domain@1/hosting/file-manager/ and certain other files, which makes it easier for remote attackers to obtain sensitive information by reading (1) web-server access logs or (2) web-server Referer logs, related to a "cross-domain Referer leakage" issue.
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Analysis
by VulDB Data Team • 01/25/2018
The vulnerability identified as CVE-2011-4759 affects Parallels Plesk Small Business Panel version 10.2.0 and represents a significant information disclosure flaw that exploits cross-domain Referer header leakage mechanisms. This vulnerability specifically manifests when the web application processes GET requests containing query strings directed at particular paths including client1/domain1/hosting/file-manager/ and related endpoints. The flaw stems from the application's improper handling of HTTP Referer headers, which are automatically included by web browsers when making requests to external resources. When users navigate to specific administrative interfaces within the Plesk panel, the application inadvertently includes external links in generated web pages that reference the originating domain through the Referer header mechanism.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP request parameters and the subsequent generation of web content that contains external references. When a user accesses the vulnerable paths within the Plesk interface, the system creates web pages that include external links pointing to resources on other domains. These links cause web browsers to automatically append Referer headers containing the originating URL to subsequent requests made to external domains. This behavior creates a scenario where sensitive information about the internal network structure and administrative access patterns becomes visible through log analysis of web server requests.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data that can be leveraged for further attacks. Attackers can exploit this flaw by analyzing web-server access logs or Referer logs to extract sensitive information about the internal domain structure, specific administrative interfaces being accessed, and potentially the presence of other internal services. This information leakage creates a pathway for attackers to understand the target environment's attack surface and plan more sophisticated attacks. The vulnerability aligns with CWE-200, which describes information exposure through improper information gathering practices, and demonstrates how seemingly innocuous logging mechanisms can become attack vectors.
From a security posture perspective, this vulnerability represents a classic example of how web application design flaws can create unintended information disclosure channels. The issue is particularly concerning in environments where multiple domains are managed through a single Plesk panel, as the Referer leakage can expose relationships between different hosted domains and their administrative access patterns. The cross-domain nature of the vulnerability means that information can be leaked to any external domain that the application links to, making it difficult to contain the impact. This flaw can be categorized under ATT&CK technique T1083, which involves discovering system information through reconnaissance activities that leverage information leakage mechanisms.
The mitigation strategies for this vulnerability should focus on implementing proper input validation and output encoding for web application responses. Administrators should ensure that all generated web content properly sanitizes external link references and does not inadvertently include sensitive information in Referer headers. Configuration changes to web servers should include disabling or limiting the inclusion of Referer headers for sensitive administrative interfaces, and implementing proper access controls that prevent unauthorized access to vulnerable paths. Regular security audits of web application code should include checks for similar information leakage patterns, and organizations should consider implementing web application firewalls to monitor and filter potentially malicious requests that could exploit this vulnerability. The vulnerability also underscores the importance of maintaining up-to-date security patches and implementing comprehensive monitoring solutions that can detect unusual Referer header patterns in web server logs.